This invention relates to graphite materials and more particularly to graphite fibers. High thermal and electrical conductivity graphite fibers are being investigated and tested for suitability in applications such as electronic packaging and space-based panels and structural components. The efficacy of the fibers and fiber-based composites for thermal management is directly proportional to the thermal conductivity (or thermal diffusivity) of the fibers. The magnitude of the thermal diffusivity is related to the orientation of the graphite planes along the fiber axis, crystalline grain size, and other similar material parameters. The electrical conductivity of these fibers can be measured and the thermal conductivity of bulk composites can be measured, but currently there does not exist the ability to measure the thermal conductivity of individual fibers, especially with a means that is suitable for the factory floor.